The article says it uses a GC thread. So perhaps it does fully concurrent GC, with no main-thread pauses whatsoever. Your skepticism is very justified, however

The article says it uses a GC thread. So perhaps it does fully concurrent GC, with no main-thread pauses whatsoever. Your skepticism is very justified, however - I would like to see the various existing GC benchmarks and GC latency benchmarks working with no pauses, to believe this.